Population Growth and Resource Availability (3.5)
Size (N)
- total # of individuals in a given area at a given time
- larger size (N)
- safer from population decline
Density
- number of individuals/area
- Higher density
- higher competition, possibility for disease outbreak, possibility of depleting food source
Distribution
- how individuals in a population are spaced out compared to each other
- random: trees
- uniform: territorial animals
- clumped: herd/group animals
Sex Ratio
- ratio of males to females
- closer to 50:50 ideal for breeding
- die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth
Density-Dependent-Factors
- factors that influence population growth based on size
- Examples
- food
- light
- competition for habitat
- water
- disease
- All these things limit population growth based on their size
Density-Independent Factors
- factors that influence population growth independence of their size.
- examples
- natural disasters
- floods
- hurricane tornado
- fire
- It doesn’t matter how big or small a pop. is, natural disasters limit them both
Ex. of Density-Dependent Factor
Food is a density dependent factor. (also a limiting resource)
When twice as much food was added to the dish, both species increased carrying capacity by about 2x
Biotic Potential
Max potential growth rate with no limiting resources
May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)
Biotic potential
- exponential growth
Logistic growth
initial rapid growth, then limiting factors limit pop. to K
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